1. Field of the Invention
The present invention relates to a composition for high pressure casting slip, a high pressure casting slip prepared by the composition and a method of preparing the composition and slip.
2. Prior Art
In Japanese Patent Laid-open Publication No. 4-48604, there is disclosed a method of molding a ceramic article by slip-casting, wherein a suspension of casting slip under pressure is poured into a porous mold so that a difference in pressure between the interior and exterior of the mold causes water of the slip to discharge through the porous walls of the mold and solid matter in the slip is deposited on the internal walls of the mold and formed in a desired shape. The molding method is useful to form a ceramic article of complicated shape, and the cost of equipment for the molding method is inexpensive. For this reason, heretofore, the molding method has been adapted to form a mold body for tableware, flower vases, household potterys and the like. In the molding method, the casting slip is prepared from a first starting powder in the form of one or plural powder raw materials selected from the group consisting of feldsputhic material, silicate material, alumina material, porcelain stone, roseki and the like and second starting powder in the form of one or plural powder raw materials selected from the group consisting of Gairome silica sand, kaolin, Kibushi clay, burned clay and the like. The first starting powder is used to form the frame of the mold body, and the second starting powder is used to form the frame of the mold body and is adapted as a plastic agent.
The first and second starting powders are cast with water into a ball mill and ground in a wet condition. Simultaneously, the starting powder is mixed uniformly in the ball mill. To enhance the efficiency of grinding and mixing in a wet condition, it is required to apply an appropriate viscosity to the mixture in the ball mill. If the viscosity of the mixture is high in excess, it will become impossible to grind and mix the starting powder. If the viscosity of the mixture is low in excess, the grinding efficiency will noticeably decrease. In the grinding and mixing process, it is preferable that an amount of water in the mixture is, in general, in a range of 45 to 55% by weight. To effect optimal fluidity of the slip during the casting process, it is preferable that the water content of the slip is in a range of 30 to 40% by weight. In the case that the slip with such a water content is used for the slip casting, the water content of the finished mold body becomes about 20% by weight.